Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2020

Asset Retirement Obligation Disclosure [Abstract]

Reconciliations of the Company's ARO liability

Reconciliations of the Company’s asset retirement obligations are as follows:

	December 31,
	2020		2019
	(Dollars in millions)
Balance at beginning of period	$	752.3	$	750.2
Liabilities settled or disposed	(38.4)		(47.7)
Accretion expense	56.0		54.1
Revisions to estimates	(41.7)		(4.3)
Balance at end of period	$	728.2	$	752.3
Less: Current portion (included in “Accounts payable and accrued expenses”)	77.7		98.2
Noncurrent obligation (included in “Asset retirement obligations”)	$	650.5	$	654.1
Balance at end of period — active locations	$	471.8	$	525.4
Balance at end of period — closed or inactive locations	$	256.4	$	226.9